Surface Diffusion and Dissolution Kinetics in the Electrolyte–Metal Interface

Abstract

Modeling of dealloying has often used a local bond-breaking approach to define the energy barrier to simulate dissolution and surface diffusion. The energy barriers are tacitly assumed to be independent of the local solution chemistry at the metal/solution interface. In this work, an interaction energy parameter is added to the local bond-breaking model that accounts for the species-specific physics of the actual atom-water molecule, atom-ion interactions and allows complex atomistic behavior to be abstracted in the modeling of the diffusion and dissolution processes. Variations in the interactions of the electrolyte components with the metal atoms led to the prediction of different surface morphologies on a binary alloy sample surface that mirror the behaviors experimentally observed in dealloying experiments in Au–Cu alloys including the formation of Au-enriched surface islands at applied potentials below the critical potential and three-dimensional porosity at applied potentials above the critical potential.

Ligament coarsening in nanoporous gold: Insights from positron annihilation study

“…The morphological view as shown in the figure is very close to the earlier experimental observations 13,15 and theoretically simulated nanoporous microstructure. 4,16 To estimate the changes in the ligament and pore sizes with annealing temperature, we have analyzed the SEM images with the support of the ImageJ software. Figures 1(b) and 1(c) show, respectively, the variation in the ligament diameter, L and the ratio of area in the pores to the ligaments, A p /A l as a function of annealing temperature.…”

Apparent Inverse Gibbs-Thomson Effect in Dealloyed Nanoporous Nanoparticles

“…Our model here is a draws on the model introduced in Ref [16] and uses a simple bond-breaking model to capture the generic morphological evolution physics occurring over experimental timescales. Specifically, rates for surface diffusion (of both silver and gold) and dissolution (of only silver) at an electrochemical potential φ are given by the expressions [1,15,15,17]; the parameters also successfully model coarsening in nanoporous nanoparticles [10] that agree with timescales of experimental studies of coarsening of nanoporous gold (which we note are generally much longer than any of the timescales discussed in this work) [18]; and recently an experimental measurement of the activation barrier for dissolution of Ag from a terrace site of a Ag/Au alloy was measured and found to be consistent with a bond energy between 0.1-0.2 eV [19]. compositions were chosen to be representative of the composition range typically found in porosity-forming dealloying systems [15].…”

Emerging Science and Research Opportunities for Metals and Metallic Nanostructures

“…87,88 Such fundamental physical phenomena inform slightly higher-level phenomena such as nucleation and growth of nanoparticles, [89][90][91] morphological stability, 92,93 and corrosion. 94 Modeling methods, such as first-principles models of the metal/electrolyte interface 95 and characterization tools, such as in situ TEM, 96 are in their infancy.…”